SEASONAL DIMORPHISM OF LEPIDOPTERA. 77 



2. The Neapolitan larvae reared at Freiburg at a room tem- 

 perature produced 8 well-developed, 13 medium to slight. 



3. The Neapolitan pup?e developed at Freiburg in the re- 

 frigerator produced 15 specimens with medium to slight tails, 

 and 11 specimens with them entirely wanting. 



Consequently the impression of this character appears to be 

 connected with the warmth, which is operating during the pupal 

 development, as it increases in direct proportion wdth the 

 warmth. 



II. Experiments with Pieris napi, 1887. 



Five females, taken in the neighbourhood of Freiburg (at 

 St. Peter), laid a number of eggs on Sisymbrium alliariay under a 

 gauze bag, on June 8th, 1887. The emergence of the larvae 

 followed at 21-22° C. on June 14th, and the larv^, which fed on 

 Sisymhriam, pupated at 21-22*5° C. in a room between June 

 30th and July 2nd. The pupse were divided into two lots. 



First experiment ivith napi. — The pupae at first remained in a 

 room at the summer temperature, 22-25° C, at which the 

 emergence should have followed after 9 days, as was ascertained 

 by experiment with one pupa. In order now to decide, whether 

 the alteration of the summer form into the winter form would 

 still take place, if cold first occurred in the last days of the pupal 

 period, consequently at the time of the formation of colour, 45 

 pupae were brought into the refrigerator on July 7th, i. e. 6-8 

 days following pupation. Development was now delayed by the 

 lower temperature, 7-11° C. ; but of the 35 butterflies, which 

 emerged between July 13th and 22nd in the refrigerator, 26 were 

 of the pronounced summer form ; only 10 exhibited stronger 

 green powdering of the veins below,* yet without possessing the 

 rest of the characters of the winter form, with the exception of 

 the deep black powdering of the bases of the wings on the upper 

 side, which occurred among all the males (6) ; while the shape 

 of the wings, theii* larger size, and the white powdering of the 

 abdomen distinguished them as the summer form. Moreover 

 the specimen, which pupated in the room and developed at 

 22-25° C, possessed an entirely similar mixture of characters. 



On July 24th the pupae which had not yet emerged were 

 brought into the incubator at 29*2° C. ; however, only 3 more 

 butterflies of the summer form emerged on the 25th ; the rest 

 first emerged in the folloiciny year. They were hybernated in 

 the cellar, and placed in a room in April. Then 12 more butter- 

 flies emerged between April 29th and June 2nd, all of an 

 exquisite winter form ; all smaller than the specimens of the 

 same brood, which had emerged in the year 1887. 



at 25° C. 



'' There was a specimen very similar to this, whose pupa had developed 



